CN110959052B

CN110959052B - Method and apparatus for producing nonwoven fabric

Info

Publication number: CN110959052B
Application number: CN201880049773.5A
Authority: CN
Inventors: 大谷进一; 下田泰久; 福永昭人
Original assignee: Fujifilm Corp
Current assignee: Fujifilm Corp
Priority date: 2017-07-25
Filing date: 2018-07-03
Publication date: 2022-02-08
Anticipated expiration: 2038-07-03
Also published as: KR102281702B1; WO2019021757A1; JP6840854B2; JPWO2019021757A1; TW201908545A; KR20200020897A; CN110959052A

Abstract

The invention provides a method and a device for manufacturing a non-woven fabric, which can restrain the thinning of the side part of a long non-woven fabric and the enlargement of the manufacturing device. A nonwoven fabric manufacturing apparatus (10, 80) manufactures a nonwoven fabric (11) by discharging a solution (23) from nozzles (31 a-31 e) in a state where a voltage is applied between a collecting material (43) and the nozzles (31 a-31 e). The nozzles (31 a-31 e) are arranged side by side in the width direction of the collecting material (43) and the charging belt (37). Extension members (71, 81) are provided on the outer side of the nozzles (31a, 31e) at a distance from the tips (31D) of the nozzles (31a, 31 e). The extension members (71, 81) are charged with electricity having the same polarity as the nozzles (31a, 31e), and cause the solution (23) facing the trapping material (43) to approach the inside in the width direction.

Description

Method and apparatus for producing nonwoven fabric

Technical Field

The invention relates to a method and a device for manufacturing non-woven fabric.

Background

For example, there is a nonwoven fabric formed of so-called nanofibers having a nanometer-scale diameter of several nanometers or more and less than 1000 nm. As a method for producing a nonwoven fabric formed of nanofibers, there is a method using an electric field spinning method (also referred to as an electrospinning method or an electrodeposition method). This method is carried out using an electrospinning device having a liquid discharge unit, a collector, and a power supply (hereinafter referred to as "1 st power supply"), and by applying a voltage between the liquid discharge unit and the collector by the 1 st power supply, for example, the liquid discharge unit is positively charged and the collector is negatively charged. In a state where a voltage is applied, a solution in which a nanofiber material (hereinafter, referred to as a nanofiber material) is dissolved in a solvent is discharged from an opening of a liquid outlet portion. The solution discharged from the liquid outlet portion is induced in the collector to form nanofibers, and the nanofibers are collected as a nonwoven fabric on the collector.

Patent document 1 describes the following technique: a space electric field control part for controlling an electric field is arranged between the liquid outlet part and the collector, thereby arbitrarily changing the pattern and/or shape of a structure such as a non-woven fabric formed by nano fibers. The space electric field control unit includes, for example: a 2 nd power supply which changes a spatial electric field according to a potential difference, different from the 1 st power supply which applies a voltage to the liquid discharge part and the collector; and a space electric field control electrode for controlling the space electric field. The space electric field control electrode controls the flight direction of the nanofibers toward the collector by applying a controlled voltage from the 2 nd power supply.

However, there is a demand for making a nonwoven fabric formed of nanofibers long. The reason is as follows: by producing the nonwoven fabric in a long size, for example, by cutting it alone, sheet-like nonwoven fabrics of various sizes can be obtained, and thus the use is expanded. In this regard, patent document 2 describes the following technique: the nonwoven fabric is made long by moving the long collector in the longitudinal direction and discharging the solution from each of the plurality of openings of the liquid outlet portion. The plurality of openings are formed in an array in the longitudinal direction of the collector. In patent document 2, an electrode extending in the direction of arrangement of the plurality of openings is provided, and the flight path of the solution discharged from the liquid outlet portion is extended by the electrode with respect to the length of a straight line virtually connecting the openings and the collector, that is, the distance between the liquid outlet portion and the collector. This increases the amount of solvent volatilized from the solution.

Prior art documents

Patent document

Patent document 1: japanese patent laid-open publication No. 2009-024292

Patent document 2: japanese patent laid-open publication No. 2011-208340

Disclosure of Invention

Technical problem to be solved by the invention

However, according to the technique described in patent document 2, even if the nanofibers are uniform, it is difficult to control the trapping area of the nanofibers on the collector and to equalize the amount of trapping in the trapping area. Therefore, the thickness of the obtained long nonwoven fabric is easily reduced in the width direction at the side portions than at the central portion. In the technique described in patent document 2, since the plurality of openings of the liquid discharge portion are arranged in the longitudinal direction of the collector, the width of the nonwoven fabric to be obtained is limited. In this regard, in order to make the nonwoven fabric wider, it is considered in patent document 2 to form a plurality of openings aligned in the width direction of the collector. However, even in the case where a plurality of openings are thus formed in a side-by-side arrangement in the width direction of the collector, the side portions in the width direction also result in becoming thinner than the central portion. When the side portions are thinner than the central portion in this manner, the side portions remain as peeling residue on the collector when the nonwoven fabric is peeled from the collector.

In this regard, the technique described in patent document 1 has a certain effect on the control of the collection area by controlling the spatial electric field to control the flight direction of the nanofibers toward the collector. However, the 2 nd power supply for controlling the spatial electric field must apply a high voltage, which results in an increase in the size of the manufacturing apparatus.

Accordingly, an object of the present invention is to provide a method and an apparatus for producing a nonwoven fabric, which can suppress the thinning of the side portion of a long nonwoven fabric and the increase in size of the production apparatus.

Means for solving the technical problem

The nonwoven fabric production method of the present invention includes a liquid discharge step and a collection step, and produces a nonwoven fabric formed of nanofibers by discharging a solution in which a nanofiber material is dissolved in a solvent from each of a plurality of nozzles toward a collector in a state where a voltage is applied between the collector and the plurality of nozzles. In the liquid discharge step, the solution is discharged from the tip of each of a plurality of nozzles arranged side by side in the width direction of a long collector moving in the longitudinal direction. In the collecting step, the solution discharged from the nozzle is collected as a nonwoven fabric in a collector. The end edge of the solution facing the collector in the width direction is brought closer to the inner side of the collector in the width direction by extending the member. The extending member is provided outside the outermost nozzle that is outermost in the width direction among the plurality of nozzles, is provided at a distance from the tip of the outermost nozzle, and extends toward the collector. The extension member is charged with electricity of the same polarity as the plurality of nozzles. The extension member is electrically connected to the plurality of nozzles by electrically connecting the nozzles and the extension member or by connecting the nozzles and the extension member in parallel to a power source for applying a voltage.

It is preferable that the inner side surface of the extension member in the width direction of the collector gradually approaches the center in the width direction of the collector as going from the outermost nozzle toward the collector.

Preferably, the distance between the extension member and the tip of the outermost nozzle is 5mm or more.

Preferably, the extension member is formed of an acrylic resin or a fluororesin.

Preferably, the nanofiber material is at least any one of cellulose triacetate, cellulose diacetate, cellulose propionate, cellulose butyrate, cellulose acetate propionate, cellulose nitrate, ethyl cellulose, and carboxymethyl ethyl cellulose.

The nonwoven fabric manufacturing apparatus of the present invention includes an elongated collector, a plurality of nozzles, a power supply, and an extending member, and discharges a solution in which a nanofiber material is dissolved in a solvent from the tip of each of the plurality of nozzles toward the collector in a state where a voltage is applied between the collector and the plurality of nozzles, thereby manufacturing a nonwoven fabric formed of nanofibers. The collector moves in the long side direction. The plurality of nozzles are arranged side by side in the width direction of the collector. The power supply applies a voltage between the nozzle and the collector. The extension member is provided outside the outermost nozzle in the width direction of the plurality of nozzles, is spaced apart from the outermost nozzle, and extends toward the collector. The extension member is charged with electricity of the same polarity as the plurality of nozzles. The extension member is electrically connected to the nozzles or is connected to a power supply in parallel with the nozzles, thereby being charged with the same polarity as the plurality of nozzles.

Preferably, an inner surface of the extension member in the width direction of the collector is gradually closer to a center of the collector in the width direction from the outermost nozzle toward the collector.

Effects of the invention

According to the present invention, a long nonwoven fabric can be manufactured in which the size of the manufacturing apparatus is suppressed from increasing and the side portions are suppressed from becoming thinner.

Drawings

Fig. 1 is a schematic view of a nonwoven fabric production apparatus.

FIG. 2 is a schematic view of a nonwoven fabric manufacturing apparatus.

Fig. 3 is a schematic view of a nonwoven fabric production apparatus.

FIG. 4 is a schematic view of a nonwoven fabric manufacturing apparatus.

Detailed Description

Fig. 1 is a schematic view of a nonwoven fabric production apparatus 10 according to an embodiment of the present invention. The nonwoven fabric manufacturing apparatus 10 is used to manufacture a nonwoven fabric 11. The nonwoven fabric 11 can be used as, for example, a wiping cloth, a filter cloth, a medical nonwoven fabric (referred to as a drape) with which a wound or the like is in contact, or the like.

The nonwoven fabric 11 is formed of nanofibers 12, and the nanofibers 12 are formed by an electrospinning method. The diameter of the nanofibers 12 is in the range of 50nm to 2000nm, and in the present embodiment is approximately 400 nm.

The nonwoven fabric manufacturing apparatus 10 is connected to the solution preparation section 21 via a pipe 22. The solution preparation unit 21 is used to prepare a solution 23 for forming the nanofibers 12. The solution preparation unit 21 prepares (prepares) a solution 23 by dissolving a nanofiber material 25 constituting the nanofibers 12 in a solvent 26 for the nanofiber material. The solution 23 prepared by the solution preparation unit 21 is guided to the nonwoven fabric manufacturing apparatus 10 through the pipe 22. The solution 23 is supplied to the nonwoven fabric production apparatus 10 by a pump 27 provided in the pipe 22.

The nonwoven fabric manufacturing apparatus 10 forms nanofibers by an electrospinning method, and manufactures a nonwoven fabric from the nanofibers. The nonwoven fabric manufacturing apparatus 10 includes a liquid outlet section 30 for discharging the solution 23. The liquid discharge portion 30 has 5 nozzles 31a to 31e (see fig. 2) as described later, and only 1 nozzle 31a is shown in fig. 1. In the following description, the nozzle 31 is described as the nozzle 31 without distinguishing the nozzles 31a to 31 e. The solution preparation section 21 is connected to one end (hereinafter, referred to as a base end) 31P of the nozzle 31 of the nonwoven fabric manufacturing apparatus 10, and thereby the solution 23 is supplied to the nozzle 31. The other end (hereinafter referred to as tip) 31D of the nozzle 31 is formed with an opening (not shown) through which the solution 23 is discharged, and the solution 23 is discharged through the opening.

The nonwoven fabric manufacturing apparatus 10 further includes a collecting section 32, a power source 33, and an extension member 71. The collection unit 32 includes a charging belt 37, a rotating unit 38, a supply unit 41, and a winding unit 42. The power supply 33 applies a voltage to the nozzle 31 of the liquid discharge portion 30 and the charging belt 37 of the trap portion 32, thereby charging the nozzle 31 to the 1 st polarity and charging the charging belt 37 to the 2 nd polarity having the opposite polarity to the 1 st polarity. The solution 23 is charged to the 1 st polarity by passing through the charged nozzle 31, and is discharged from the nozzle 31 in a charged state (liquid discharge step).

The charging belt 37 is used to attract the solution 23 discharged from the nozzle 31 and to collect the formed nanofibers 12 as the nonwoven fabric 11. In this example, the charging belt 37 collects the nanofibers 12 on the long collecting member 43 supplied from the supply unit 41, and the collecting member 43 functions as a collector in conjunction with the charging belt 37. The charging belt 37 is an endless belt formed in an endless shape from a metallic belt-like material. The charging belt 37 may be made of a material charged by applying a voltage from the power supply 33, and may be made of, for example, stainless steel. The collecting member 43 is a band-shaped aluminum sheet in the present embodiment, but the material is not limited if it is charged to the 2 nd polarity via the charging belt 37 and does not inhibit the solution 23 from being attracted by the charging belt 37.

In the present embodiment, the nozzle 31 is positively charged (+), and the charging belt 37 is negatively charged (-), however, the polarity of the nozzle 31 and the charging belt 37 may be reversed. By these charging, a substantially conical taylor cone (not shown) of the solution 23 is formed at the tip 31D of the nozzle 31, and the solution 23 is directed from the taylor cone as a spinning jet flow toward the charging belt 37 to become the nanofibers 12. The nanofibers 12 are formed into a nonwoven fabric on the trapping material 43.

The distance L1 between the nozzle 31 and the trapping material 43 varies depending on the types of the nanofiber material 25 and the solvent 26, the mass ratio of the solvent 26 in the solution 23, and the like, and is preferably in the range of 100mm to 300mm, and is 150mm in the present embodiment.

The rotating portion 38 is constituted by a pair of

rollers

46 and 47, a motor 48, and the like. The charging belt 37 is horizontally wound around a pair of

rollers

46, 47. A motor 48 disposed outside the spinning chamber 51 is connected to the shaft of one of the rollers 46, and the roller 46 is rotated at a predetermined speed. By this rotation, the charging belt 37 moves in the longitudinal direction so as to circulate between the

rollers

46 and 47. In the present embodiment, the moving speed of the charging belt 37 is set to 10 cm/hour, but the present invention is not limited thereto.

The supply portion 41 has an output shaft 41 a. The output shaft 41a is provided with a catch material roller 52. The trapping material roll 52 is configured such that the trapping material 43 is wound around the winding core 53. The take-up section 42 has a take-up shaft 56. The winding shaft 56 is rotated by a motor (not shown), whereby the trapping material 43 moves in the longitudinal direction, and the trapping material 43 in a state where the nonwoven fabric 11 is formed is wound around a winding core 57 provided in the winding shaft 56. The solution 23 is continuously discharged from the nozzle 31 toward the moving collector 43, whereby the nanofibers 12 are collected on the collector 43, and the nonwoven fabric 11 is continuously produced (collecting step). The long nonwoven fabric 11 obtained by continuous production is peeled off from the trapping material 43, and cut into a size and a shape corresponding to the application.

In this example, the rotation speed of the take-up shaft 56 is equal to the rotation speed of the roller 46, and the trapping material 43 is moved by the rotation of the take-up shaft 56, but the trapping material 43 may be placed on the charging belt 37 and moved by the movement of the charging belt 37.

Instead of using the trapping material 43, the nanofibers 12 may be trapped directly on the charging belt 37. At this time, the charging belt 37 functions as a collector. However, the nonwoven fabric 11 may be adhered and not easily peeled off depending on the material forming the charging belt 37, the surface state of the charging belt 37, and the like. Therefore, as in the present embodiment, it is preferable to guide the trapping member 43 to which the nonwoven fabric 11 is less likely to adhere to the charging belt 37 and trap the nanofibers 12 in the trapping member 43.

The liquid discharge unit 30 includes a nozzle 31, a conducting member 61, and a container 62. The nozzle 31 is disposed in the container 62 in a posture in which the tip 31D faces upward. That is, the nozzle 31 is set in a state in which the tip 31D of the discharge solution 23 is directed to the charging belt 37 disposed above the nozzle 31.

The container 62 contains a solvent 63 that dissolves the nanofiber material 25. The solvent 63 is a liquid. Since the solvent 63 is vaporized, the tip 31D is disposed in an environment including the solvent 63 in a gaseous state. Hereinafter, the solvent in a gaseous state is referred to as a solvent gas 66. In the present embodiment, the nozzle 31 is attached so as to penetrate the bottom of the container 62, but the method of attaching the nozzle 31 to the container 62 is not limited to this. For example, the base end 31P of the nozzle 31 may be connected to a hose (not shown) penetrating the bottom of the container 62, and the nozzle 31 may be attached to the container 62 through the hose. The solvent 63 may dissolve the nanofiber material 25. The solvent 63 is, for example, the same solvent as the solvent 26.

Since the tip 31D of the nozzle 31 faces upward, even when the solution 23 is coagulated at the tip 31D, the coagulated product does not fall onto the nanofibers 12 accumulated on the charging belt 37. Further, by disposing the distal end 31D in an environment containing the solvent 63, the adhesion of the above-mentioned coagulated product to the distal end 31D can be suppressed, and the clogging of the distal end 31D can be suppressed. As a result, the nanofibers 12 can be produced efficiently in a good yield.

The pipe 22 for guiding the solvent 63 fed from the pump 27 is connected to the container 62. The container 62 is provided with a level sensor 67 for detecting the level of the liquid surface 63s of the solvent 63, and the height of the liquid surface 63s is adjusted by controlling the amount of the solvent 63 injected into the container 62 based on a detection signal from the level sensor 67. The liquid surface 63s is lower than the front end 31D of the nozzle 31 disposed in the container 62. That is, the nozzle 31 is provided in the container 62 in a state where the tip 31D protrudes from the liquid surface 63 s. Thus, the solvent gas 66 allows the tip 31D to be placed in an environment containing the solvent 63, and the tip 31D is more reliably prevented from being clogged.

The distance from the liquid surface 63s of the tip 31D is preferably in the range of 2mm to 15mm, and is 5mm in the embodiment. Since the distance is 2mm or more, the liquid solvent 63 does not gradually rise to the tip 31D of the nozzle 31 as compared with the case of less than 2mm, and therefore spinning is performed more stably, and since the distance is 5mm or less, the solution 23 is discharged from the nozzle 31 in an environment with a high solvent gas concentration as compared with the case of more than 15mm, and therefore spinning is performed more stably.

A temperature sensor 68 for detecting the temperature of the solvent 63 is provided in the container 62, and the temperature of the solvent 63 is adjusted by a temperature adjusting unit (not shown) based on a detection signal of the temperature sensor 68. The temperature of the solvent 63 is lower than the boiling point of the solvent 63 by 5 ℃ or more, that is, preferably lower than the boiling point of the solvent 63 by at least 5 ℃, and in the present embodiment, lower by 5 ℃. The container 62 and the solvent 63 are not necessarily used.

The conducting member 61 is disposed below the container 62. The conducting member 61 is electrically connected to the base end 31P side of the nozzle 31 projecting downward of the container 62. The power supply 33 is connected to the conducting member 61, and applies a voltage to the nozzle 31 via the conducting member 61. The method of applying the voltage to the nozzle 31 is not limited to this. For example, a voltage may be applied to the nozzle 31 by connecting a power supply 33 to the nozzle 31. The voltage to be applied is preferably 2kV or more and 40kV or less, and is preferably as high as possible in this range from the viewpoint of forming the nanofibers 12 to be thin. In the present embodiment, the applied voltage is set to 30 kV.

In this example, the nozzle 31 is disposed in a posture in which the tip 31D faces upward, and the charging belt 37 is disposed above the nozzle 31, but the posture of the nozzle 31 and the positional relationship between the nozzle 31 and the charging belt 37 are not limited to this. For example, when the nozzle 31 is disposed in a posture in which the tip 31D faces downward and the charging belt 37 is disposed below the nozzle 31, the container 62 and the solvent 63 are not used.

An extension member 71 extending from the nozzle 31 side toward the collecting member 43 and the charging belt 37 is provided between the liquid outlet portion 30 and the conveyance path of the collecting member 43 on the charging belt 37. The extension member 71 is a plate-like member disposed along the longitudinal direction of the charging belt 37 and the trapping member 43. The extension member 71 is provided in an upright posture with respect to the belt surface of the charging belt 37 on the nozzle 31 side and the trapping material 43 on the charging belt 37. The extension member 71 is connected to the power supply 33 in parallel with the nozzle 31. The extension member 71 is described in detail later with reference to another drawing.

The spinning chamber 51 accommodates, for example, the liquid outlet portion 30, a part of the collecting portion 32, an extension member 71, and the like. In the spinning chamber 51, a nozzle 31 and a container 62 are arranged at the lower part, and a trap part 32 is arranged at the upper part. The spinning chamber 51 is configured to be hermetically sealable, thereby preventing leakage of solvent gas or the like to the outside. The solvent gas is a gas in which the solvent 26 of the solution 23 is vaporized.

As shown in fig. 2, the nozzles 31a to 31e are arranged in a state of being spaced apart from each other in the width direction of the charging belt 37. Since the width direction of the trapping material 43 coincides with the width direction of the charging belt 37, these directions will be collectively referred to simply as "width direction" in the following description. The phrase "arranged side by side in the width direction" means that the charging belt 37 and the trapping material 43 are arranged at positions slightly shifted in the longitudinal direction when they are arranged to have a component in the width direction. In the present embodiment, when all of the nozzles 31a to 31e are positioned within 50mm in the longitudinal direction, a mode of being arranged side by side in the width direction is acceptable. Among the nozzles 31a to 31e arranged in this order in the width direction, the nozzle arranged outermost in the width direction is referred to as the outermost nozzle. The outermost nozzles in this example are nozzle 31a and nozzle 31 e.

In this example, the number of the nozzles 31 is set to 5, but the number of the nozzles 31 is not limited to 5, and may be 2 or more. In this example, the plurality of nozzles 31 are arranged in parallel in the width direction, and thus the openings for discharging the solution 23 are arranged in parallel in the width direction, but an integrated liquid discharge member formed so that a plurality of openings are arranged in parallel in the width direction may be used instead of the plurality of nozzles 31.

When the distance L2 is 1mm or more when the distance between the openings of the tip 31D is L2, the spinning is performed more stably by suppressing the discharge between the nozzles 31 than in the case where the distance is less than 1mm, and the device can be further downsized than in the case where the distance is greater than 20mm because the distance L2 is 20mm or less. The distance L2 is more preferably in the range of 3mm to 10mm, and is set to 5mm in the present embodiment. The distance L2 between the openings is the distance between the centers of the adjacent openings.

The angle θ of the nozzle 31 with respect to the liquid surface 63s will be described. Here, θ when the longitudinal direction of the nozzle 31 is horizontal is 0 °, and θ when the nozzle is vertically upward is 90 °. The nozzle 31 is directed upwards, so 0 < theta < 90 deg. As the angle θ approaches 90 °, the voltage required to move the solution 23 discharged from the nozzle 31 to the charging belt 37 decreases. As the voltage applied to the nozzle 31 is smaller, vaporization of the solvent 26 on the tip 31D is more suppressed, and clogging of the nozzle 31 is further suppressed. Therefore, the angle θ is preferably in the range of 45 ° to 90 °, and in the present embodiment, the angle θ is set to 90 °.

The tips 31D of the plurality of nozzles 31a to 31e are more preferably oriented in the same direction. This makes it possible to obtain a nonwoven fabric 11 having a more uniform mass per unit area, i.e., a more uniform thickness. The mass per unit area means the mass per unit area of the nonwoven fabric.

The extension member 71 is provided to bring the position where the nanofibers 12 formed from the solution discharged from the outermost nozzles are captured by the capture material 43 closer to the inner side in the width direction. As described above, since the extension member 71 is connected to the power source 33 in parallel with the nozzle 31, the widthwise inner surface 71s has the 1 st polarity which is the same polarity as the nozzle 31 a. In the present embodiment, the polarity of the extension member 71 is positive (+) because the nozzle 31 is positively charged (+). When the nozzle is charged negatively (-), the polarity of the extension member 71 becomes negative (-). As described above, the extension member 71 is formed in a plate shape, but is not limited to a plate shape, and may be formed in a block shape, for example. Even in the case of the block shape, the widthwise inner surface 71s may be charged with the same polarity as the nozzle 31 a. The one extending member 71 is disposed on the outer side in the width direction than the one nozzle 31a of the pair of outermost nozzles, and is provided in a state of being spaced apart from the nozzle 31 a. Similarly, an extension member 71 is provided on the other nozzle 31e of the pair of outermost nozzles, and since the extension member 71 is connected to the power supply 33 in parallel with the nozzle 31, the 1 st polarity having the same polarity as that of the nozzle 31e is provided on the inner surface 71s in the width direction.

Since the extension member 71 is provided in a state of being separated from the respective tips 31D of the

nozzles

31a and 31e, the movement of the electric charges from the

nozzles

31a and 31e to the extension member 71 can be prevented. Therefore, the surface 71s of the charged extension member 71 and the nozzle 31 maintain the polarity, and the solution 23 is stably discharged from the nozzle 31a and the nozzle 31 e. In the extension member 71, since the surface 71s is charged with the same polarity as the

nozzles

31a and 31e, the solution 23 discharged from the openings of the tips 31D of the

nozzles

31a and 31e has the same polarity, and therefore the solution 23 heading toward the trapping material 43 from the

nozzles

31a and 31e is electrically repelled from the surface 71s and is located inward in the width direction. As a result, the formed nanofibers 12 are trapped inside the trapping material 43 in the width direction, compared to the case where the extension member 71 is not provided. Therefore, in the nonwoven fabric 11, the thickness of both side portions mainly formed by the solution 23 discharged from the

nozzles

31a and 31e can be suppressed from being reduced, and the peeling residue can be suppressed when peeling off the collecting material 43 in the subsequent step.

The extension member 71 may be formed of an insulating material, or may be formed of a conductive material. In this embodiment, the volume resistivity is set to 10⁷The material with a volume resistivity of 10 is used as insulating material⁴Materials of Ω · cm or less are considered as conductive materials. In the present embodiment, the volume resistivity is determined by measurement according to the double ring electrode method of JIS K6911.

The insulating material in the case where the extension member 71 is formed of an insulating material is preferably, for example, an acrylic resin or a fluororesin, from the viewpoint of reliably charging electricity having the same polarity as the nozzle 31. The insulating material is preferably selected from materials resistant to the solvent 26.

In the present embodiment, since a power supply common to the nozzle 31 is used, the size increase of the apparatus can be suppressed. The extension member 71 may have only the charge amount for bringing the solution 23 discharged from the

nozzles

31a and 31e of the plurality of nozzles 31a to 31e to the inner side in the width direction, and thus may be connected in parallel with the nozzles 31 to apply the voltage without using a power supply other than the power supply 33.

The distance L3 between the tip 31D of the

nozzle

31a or 31e and the extension member 71 is at least 5mm, that is, preferably 5mm or more, more preferably in the range of 5mm or more and 50mm or less, still more preferably in the range of 10mm or more and 40mm or less, and particularly preferably in the range of 15mm or more and 30mm or less.

The extension member 71 may extend from the nozzle 31 side toward the charging belt 37 and the collecting member 43. That is, the extending direction may have a component in the vertical direction in fig. 2. For example, the extension member 71 may extend in the vertical direction in fig. 2, and may extend in a direction intersecting the vertical direction as in the example shown in fig. 2. In this example, the extension member 71 is provided in a state in which the surface 71s is closer to the center in the width direction from the tip 31D of the nozzle 31a and the nozzle 31e toward the charging belt 37 and the trapping member 43. That is, the distance between the pair of extension members 71 decreases as they approach the charging belt 37 and the trapping member 43. This allows the nanofiber 12 to be trapped inside the trapping material 43 more reliably in the width direction.

The extension member 71 is preferably extended to a position as close as possible so as not to contact the moving charging belt 37 and the trapping member 43. That is, the distance L4 between the extension member 71 and the trapping member 43 is preferably set as small as possible so as not to contact the trapping member 43 that moves. The extension member 71 is used to bring the position where the nanofibers 12 formed from the solution from the

nozzles

31a and 31e are collected to the inside in the width direction, and therefore is preferably disposed in a state where the end of the surface 71s on the side of the collecting material 43 is positioned on the inside in the width direction from the side edge of the collecting material 43.

The nanofiber material 25 is preferably a polymer, and is any one of cellulose acylate, cellulose nitrate, ethyl cellulose, and carboxymethyl ethyl cellulose. More preferred cellulose acylate is triacetylcellulose, diacetylcellulose, cellulose propionate, cellulose butyrate or cellulose acetate propionate.

Examples of the solvent 26 include methanol, ethanol, isopropanol, butanol, benzyl alcohol, acetone, methyl ethyl ketone, cyclohexanone, methyl acetate, ethyl acetate, propyl acetate, butyl acetate, methyl formate, ethyl formate, hexane, cyclohexane, methylene chloride, chloroform, carbon tetrachloride, benzene, toluene, xylene, dimethylformamide, N-methylpyrrolidone, diethyl ether, dioxane, tetrahydrofuran, and 1-methoxy-2-propanol. These may be used alone or in combination depending on the kind of the nanofiber material 25. Among these, dichloromethane (boiling point: 40 ℃) is more preferable, and in the present embodiment, dichloromethane is used as the solvent 26.

The nonwoven fabric manufacturing apparatus 80 shown in fig. 3 includes an extension member 81 instead of the extension member 71 of the nonwoven fabric manufacturing apparatus 10. The power supply 33 is connected only to the roller 47 and the conduction member 61. In this example, similarly to the above-described example, the polarity of the nozzle 31 is positive (+) and the polarities of the charging belt 37 and the trapping member 43 are negative (-) by applying a voltage in a state where the conductive member 61 is positively charged (+) and the roller 47 is negatively charged (-). However, the voltage may be applied in a state where the conductive member 61 is negatively charged (-) and the roller 47 is positively charged (+). As shown in fig. 4, each of the pair of extension members 81 is formed in a plate shape bent in an L shape, and is disposed in a state where one end of the nozzle 31a side and one end of the nozzle 31e side are in contact with the conduction member 61. Thus, the extension member 81 is electrically connected to the

nozzles

31a and 31e, and therefore, the inner surface 81s in the width direction of the extension member 81 is charged with the same polarity as the

nozzles

31a and 31 e. The extension member is not limited to the L-shape in this example, as long as it is electrically connected to the nozzle 31a and the nozzle 31e so as to be charged with electricity having the same polarity as the nozzle 31a and the nozzle 31 e. For example, even in a case where a flat plate-shaped extension member 71 is used and the extension member 71 is connected to the conduction member 61 by a conductive member such as a wire, the extension member is preferably electrically connected to the nozzle 31a and the nozzle 31 e.

The extension member 81 is also extended toward the charging belt 37 and the collecting member 43 similarly to the extension member 71, and is disposed in a state of being separated from the tips 31D of the

nozzles

31a and 31 e. Therefore, the nanofibers 12 formed from the solutions from the

nozzles

31a and 31e are collected by the collecting material 43 while approaching the inner side in the width direction. The extension member 81 is also provided in a state where the surface 81s is closer to the center in the width direction from the leading ends 31D of the

nozzles

31a and 31e toward the charging belt 37 and the trapping member 43, similarly to the extension member 71. This allows the nanofibers 12 to be trapped in the trapping material 43 at a position more reliably on the inner side in the width direction.

Examples

[ example 1] to [ example 10]

A long nonwoven fabric 11 was produced by using a nonwoven fabric production apparatus 80, and examples 1 to 10 were set. As shown in table 1, in examples 1 to 10, the material of the extension member 81 and/or the distances L3 between the extension member 81 and the tips 31D of the

nozzles

31a and 31e are different from each other. The nanofiber material 25 is cellulose triacetate. As solvent 26, dichloromethane was used.

When an acrylic resin as an insulating material was used as a raw material of the extension member 81, the column of "raw material" in table 1 is described as "acrylic" and when SUS (stainless steel) as a conductive material was used, it is described as "SUS". The nozzle 31 is positively charged (+) as described above, and thus the polarity of the surface 81s of the extension member 81 is also positive (+). The column "polarity" in table 1 indicates the polarity of the surface 81s of the extension member 81.

In each example, the spinning stability of the spun nanofibers 12 and the thickness of the side portion of the obtained nonwoven fabric 11 were evaluated by the following evaluation methods and criteria. The evaluation results are shown in table 1.

(1) Stability of spinning

The spinning state from the outermost nozzles, i.e., the nozzle 31a and the nozzle 31e, was visually confirmed and evaluated by the following criteria. A and B are acceptable grades as products capable of manufacturing the nonwoven fabric 11 into a longer size, and C is unacceptable.

A: the continuous spinning time is more than 5 minutes

B: the time for continuous spinning is 1-5 min

C: the time for continuous spinning is less than 1 minute

(2) Thickness of the side part

A perpendicular line is drawn from the opening of the nozzle 31a, which is the outermost nozzle, to the trapping material 43, and the mass X per unit area of the nonwoven fabric 11 is determined for a region up to a position of 10mm from the perpendicular line in the trapping material 43 toward the side edge side. The mass X per unit area was determined by measuring the weight of a sample of 1 cm. times.1 cm with an electronic scale. Then, a perpendicular line is drawn from each opening of the

nozzles

31a and 31e to the trapping material 43, and 5 samples are obtained by sampling the trapping material 43 at 5 sites each surrounded by the perpendicular line at a size of 1cm × 1 cm. The weight of each sample was measured by an electronic scale, and the average value Y of the mass per unit area was obtained. Then, the mass ratio per unit area (unit%) calculated by (X/Y) × 100 was obtained, and the mass ratio per unit area was evaluated as the thickness of the side portion. A and B are qualified, and C is not qualified.

A: the mass ratio of the unit area is more than 90 percent

B: the mass ratio of the unit area is more than 80 percent and less than 90 percent

C: the mass proportion of the unit area is less than 80 percent

[ Table 1]

Comparative examples 1 to 3

The extension member 81 was taken out from the nonwoven fabric manufacturing apparatus 80, and a nonwoven fabric was manufactured without using the extension member 81, which is assumed as comparative example 1. Other conditions of comparative example 1 were the same as in example. Since the nonwoven fabric manufacturing apparatus used in comparative example 1 did not include the extension member 81, the columns of "raw material", "polarity", and "distance L3" in the column of "extension member" in table 1 were blank columns. In addition, comparative examples 2 and 3 were prepared by replacing the extension member 81 of the nonwoven fabric manufacturing apparatus 80 with the extension member 70. The extension member 70 in comparative examples 2 and 3 is not connected in parallel to the nozzle 31 to the power supply 33, and is positively charged (+) with the same polarity as the nozzle 31a and the nozzle 31e by coming into contact with the tip 31D of the nozzle 31a and the nozzle 31 e. Since the extension member 71 is in contact with the tip 31D, the distance L3 is 0 (zero) mm as shown in table 1.

In each comparative example, the spinning stability and the thickness of the side portion were evaluated by the same method and standard as in the examples. The evaluation results are shown in table 1. In comparative examples 2 and 3, the solution 23 was not discharged from the

nozzles

31a and 31 e.

Description of the symbols

10. 80-nonwoven fabric manufacturing apparatus, 11-nonwoven fabric, 12-nanofiber, 21-solution preparation section, 22-tubing, 23-solution, 25-nanofiber material, 26-solvent, 27-pump, 30-liquid discharge section, 31a to 31 e-nozzle, 31D-tip, 31P-base, 32-collection section, 33-power supply, 37-charging belt, 38-rotating section, 41-supply section, 41 a-output shaft, 42-winding section, 43-collection material, 46, 47-roll, 48-motor, 51-spinning chamber, 52-collection material roll, 53-winding core, 56-winding core, 57-winding core, 61-conducting member, 62-container, 63-solvent, 66-solvent gas, 67-level sensor, 68-temperature sensor, 71, 81-extension member, 71 s.81s-surface of the inner side in the width direction, L1-distance of nozzle from trapping material, L2-distance of openings from each other, L3-distance of tip of outermost nozzle from extension member, L4-distance of extension member from trapping material, angle of theta-nozzle.

Claims

1. A method for producing a nonwoven fabric, wherein a nonwoven fabric formed of nanofibers is produced by discharging a solution in which a nanofiber material is dissolved in a solvent from each of a plurality of nozzles toward a collector in a state where a voltage is applied between the collector and the plurality of nozzles,

the method for manufacturing the non-woven fabric comprises the following steps:

a liquid discharge step of discharging the solution from the tips of the plurality of nozzles arranged side by side in the width direction of the long collector moving in the longitudinal direction; and

a collecting step of collecting the solution discharged from the nozzle as the nonwoven fabric in the collector,

an extending member that is provided further to the outside than the outermost nozzle on the outermost side in the width direction among the plurality of nozzles, is provided in a state of being spaced apart from the tip of the outermost nozzle, extends toward the collector, and is charged with the same polarity as the plurality of nozzles,

electrically connecting the nozzle and the extension member, or connecting the nozzle and the extension member in parallel to a power supply for applying the voltage, thereby charging the extension member with electricity having the same polarity as the plurality of nozzles,

an inner side surface of the extension member in the width direction of the collector gradually approaches a center in the width direction of the collector as going from the outermost nozzle toward the collector.

2. The method for producing a nonwoven fabric according to claim 1,

the distance between the extension component and the front end of the outermost nozzle is more than 5 mm.

3. The method for producing a nonwoven fabric according to claim 1,

the extension member is formed of an acrylic resin or a fluororesin.

4. The nonwoven fabric production method according to any one of claims 1 to 3,

the nanofiber material is at least any one of cellulose triacetate, cellulose diacetate, cellulose propionate, cellulose butyrate, cellulose acetate propionate, cellulose nitrate, ethyl cellulose and carboxymethyl ethyl cellulose.

5. A nonwoven fabric manufacturing apparatus that manufactures a nonwoven fabric formed of nanofibers by discharging a solution in which a nanofiber material is dissolved in a solvent from the tip of each of a plurality of nozzles toward a collector in a state where a voltage is applied between the collector and the plurality of nozzles,

the nonwoven fabric manufacturing apparatus includes:

the long collector moves along the long side direction;

the plurality of nozzles are arranged side by side in the width direction of the collector;

a power supply that applies the voltage between the nozzle and the collector; and

an extending member that is provided outside the outermost nozzle of the plurality of nozzles in the width direction, is provided at a distance from the outermost nozzle, extends toward the collector, and is charged with electricity having the same polarity as the plurality of nozzles,

the extension member is electrically connected to the nozzles or is connected to the power supply in parallel with the nozzles, thereby being charged with the same polarity as the plurality of nozzles,